1. Field of the Invention
The field of art to which this invention pertains is hydrocarbon processing. Specifically, this invention relates to an improvement in the distribution of a heterogeneous fluid (gas-liquid) over the surface of a solid bed of particulates, disposed in a packed chamber, for the purpose of effecting uniform contact with the particulate bed.
2. Prior Art
Commercial processes abound which involve contacting fluid hydrocarbon and other materials with a confined bed of solid particles for the purpose of physical or chemical treatment of the fluid materials. In many of these processes, the conditions of temperature and pressure, as well as the physical characteristics of the fluids, are such that upon entry onto the particulate bed, they are substantially unvaporized or incompletely vaporized. Such processes include, among others, catalytic hydrocracking of various hydrocarbon oils, hydrodesulfurization of middle distillates, and crude oil clean-up.
In the aforementioned processes it is well known that the stream of fluids entering the contact zone comprises gaseous hydrogen, vaporized hydrocarbons and liquid hydrocarbons. It is desired that these components be intimately admixed and intermingled, as, for example, in a colloidal dispersion. This dispersion must be evenly distributed over the particulate bed so that contact with the bed is uniform. Uniform contact is necessary to utilize the particulates to their maximum efficiency and so effect the desired treatment or conversion of the flowing stream of fluids. Also, it is well known that reactions are encountered in the catalytic environments of the aforementioned processes which are exothermic, and a localized lack of hydrogen can result in regions within the particulate bed of excessively high temperatures and excessive coke deposition upon the particulate catalysts. This results from poor mixing and distribution of the gaseous, vaporous and liquid components of the feed stream. Good mixing and distribution have been found extremely difficult or impossible to achieve in mixed-phase fluid systems. It is typical in the art, because of space velocity and residence time considerations, that the particulate bed be elongated in the direction of flow. This results in contact zones in the form of vertically elongated vessels employing upflow or downflow of fluids. While flow is substantially upward or downward, it can involve segmented lateral paths or radial paths whereby the fluids traverse the particulate bed horizontally and are collected in a centerpipe for exit from the contact vessel. There are many kinds of distributing means utilized to mix and disseminate flow from the inlet point of packed chambers to the particulate beds therein, as, for example, various types of deflecting plates, perforated plates, spray nozzles, etc. However, it has been shown that the usual types of distributing means do not provide uniform flow of a mixed-phase onto the contact bed. There is evidence that the dispersed liquid coalesces rapidly, disassociating itself from the hydrogen, and thereby tending to distribute poorly and channel within the contact zone. Heavier viscous liquids tend to channel down the walls of the contact vessel, whereas less viscous liquids tend to channel in the central region of the particulate bed with the vaporized hydrocarbon and hydrogen. As a result, the temperature within the bed is non-uniform and localized hot spots occur which cause the undesirable results of non-selective hydrocracking and coke deposition.
The present invention solves these prior art problems of poor mixing and distribution. In the embodiments of my invention, the mixed-phase fluid is converted into foam, a homogeneous mixture of the fluid's components which lends itself to even distribution onto the particulate bed.